Pymatuning Reservoir, near Linesville, Pennsylvania, is known regionally as the place 'Where the Ducks Walk on the Fish', although it is actually the spillway at Pymatuning Reservoir that is home to this odd spectacle. There's a simple explanation for the phenomenon; carp collect at the base of the spillway in such numbers that ducks can cross from one side to the other and, consequently, barely touch the water.
And in the anything for a buck spirit that makes tourism the second leading industry in Pennsylvania behind farming, the site has become something of a tourist trap. There are shops along the road leading to the spillway which sell bread and souvenirs.
OK, souvenirs make sense1... but why do they sell bread?
Bread is the key to the whole phenomenon. Visitors throw scraps of stale bread into the water (there's also a fish feeding station available for people with disabilities) and the fish go into a feeding frenzy and rush to the surface to get the bread. Not to be out-done by some fish, the ducks also charge towards anyone tossing bread into the water, often walking across the backs of the fish as there is no room for them to swim.
In a lot of ways it's kind of a creepy sight. One Researcher visited there 20 plus years ago, and the site of those gaping carp mouths opening and closing near the surface of the water with ducks hopping about, putting feet inside the odd fish's mouth, is still as sharp today as it was then. Still photos really don't do it justice. A video, preferably with sound, really conveys the horror and majesty of watching ducks walk over frenzied fish for some hunks of stale bread.
Of course, you could go and visit to see the spectacle for yourself. You can get there by taking Route 6 west of Meadville, Pennsylvania, until you reach the town of Linesville, and then follow the signs to the spillway.
The lake and spillway are part of the larger Pymatuning State Park, which offers boating, fishing, swimming, and hunting, as well as camping and picnic facilities. The large lake is located along the Pennsylvania-Ohio border with about a quarter of it sitting in Ohio.